The present invention relates generally to the field of hydraulic circuits utilized in automatic transmission systems and, more particularly, to a replacement Boost Valve Assembly for use in a General Motors 4T65E transmission, which is utilized to boost hydraulic pressure during high load conditions.
Automatic transmission systems of the prior art have a hydraulic circuit sub-system which includes at least a hydraulic pump, a valve body having fluid conducting passages or circuits, input and exhaust ports formed within the fluid circuits, and a plurality of spool valves so-called because of their resemblance to sewing-thread type spools. Such valves are comprised of generally cylindrical pistons having control diameters or lands formed thereon, which alternately open and close the ports to the fluid circuits to regulate the flow and pressure of automatic transmission fluid (hereinafter xe2x80x9cATFxe2x80x9d) in order to actuate different components of the transmission. It will be understood that in describing hydraulic circuits, ATF usually changes names when it passes through an orifice or control valve in a specific fluid circuit.
In the prior art, the Line Boost Valve is acted upon by Torque Signal (hereinafter xe2x80x9cTSxe2x80x9d) pressure and operates against the Reverse Boost Valve and Pressure Regulator spring force to increase line pressure during high load conditions. The Line Boost Valve is actuated in response to changes in throttle position such as during upshifts.
The original equipment manufacture (hereinafter xe2x80x9cOEMxe2x80x9d) Line Boost Valve and Reverse Boost Valve are comprised of steel valve pistons that reciprocate within an aluminum valve sleeve. The mechanical friction of these dissimilar materials causes premature wear, leakage of torque signal pressure, and results in improper upshifting and delayed engagement upon shifting into the Reverse gear range.
Thus, the present invention has been developed to resolve this problem and other shortcomings of the prior art.
Accordingly, the present invention is a direct replacement Boost Valve Assembly for use in combination with a Pressure Regulator Valve within the valve body of an automatic transmission, which functions to boost line pressure during high load conditions in response to Torque Signal fluid pressure, which is proportional to engine torque.
The present Boost Valve Assembly is comprised of hard-anodized aluminum valve pistons, which are disposed within a wear resistant aluminum sleeve for maximum service longevity. Annular lubrication grooves in the present Boost Valve Assembly provide a lubricating film of ATF to center the valve pistons within the sleeve to ensure accurate operation and to reduce wear. The present valve sleeve also features improved inlet ports to enhance the delivery of TS fluid pressure in order to restore the function of the OEM valve body to its original factory boost ratios and specifications.
Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings.